Graphitizing electrodes.



HROULT. y emncfrnons. ION FILED PEBJO, 1910.

Patented June 11, 1912.

TIZIN Wow A .WN Q

GBAPHI APrLmAT :WITNESSES:

UNITED STATES PATENT OFFICE.

PAUL LOUIS TOUSSAINT HROULT, OF LA PRAZ, FRANCE, ASSIGNOR, BY MESNE vASSIGrNlyIENTS, TO ELECTRODE COMPANY OF AMERICA, OF vNIAGARA FALLS, NEW

YORK, A CORPORATION OF NEW YORK.

GRAPHITIZING ELECTRODS.

Specification of Letters Patent.

Patented June 11, 1912.

Application filed February 10, 1910. Serial No. 543,067.

provements in Graphitizing Electrodes, of

which the following is a specification.

rThe present invention aims to secure electrodes for electric furnaces and other uses which are of greater efficiency and economy than those heretofore used, and which can be manufactured easily and comparatively cheaply. i

The product of the invention is anelectrode or a section of an electrode having one or both ends graphitized and having another part whichisnot graphitized to the same extent as the end, being graphitized to a less degree or not at all according to the circum stances of its use.- Such an electrode or section is secured by subjecting the end of it to graphitizing conditions while avoiding the same conditions at another part of the electrode. Preferably ,thisaction is secured by arranging the electrodes or sections end to end with imperfect contact and passing' a current through them so asto cause the graphitizing of the contacting ends before vthe rest of the electrode.

It is common practice to make up comi ypound electrodes by screwing together the ends of two sections. With the sections made in accordance with this invention the carbon at 'the ends by reason of the excessive heat generated there through the (imperfect contact is easily machined andis also of highconductivity so as to minimize the tendency to make an imperfect joint at this point by the finished electrode. The middle parts of the sections are not graphitized or. at least not to the same extent as the ends. Consequently t e heat conductivity of these parts is less tian that of the ends and the llosses of heat in the furnace in which the electrodev is used are diminished. The accompanying drawings illustrate an embodiment of the invention I v Figure l is a plan partly in sectionof a furnace kat work, omitting the blanketing material. Fig. 2 is a cross section "on the line 2-2 of Fig. 11. Fig. 3 is a cross section, on a larger scale than Figs. 1 and 2 of parts of the furnace. Fig. 4 is a longitudinal sectional view of the joint connecting the ends of two sections of a compound electrode.

The furnace used is of a type similar to that covered in my application No. 523,194 for patent for 'graphitizing large electrodes. This furnace has side walls A, end walls B and a bottom C of brick work with a central longitudinal partition D atso of brick work for retaining the granular material which is used as a blanket to keep the heat in. The central partition D divides the furnace into two longitudinal compartments in which the process is carried on.

In executing the process there is arranged in each of the compartments a long line of electrodes E placed end to end with a packing F of graphite between them of such a nature and construction as to form an imperfect electrical connection between them. A current is passed through the line of electrodes of sulicient volume and intensity to create a high temperature at the end por tions of the electrodes where the contact is imperfect, with a lower' temperature at the other points; the conditions being calculated so that the end of the electrodes will be 'graphitized to the desired extent while the other parts are graphitized to a less eX- tent or not at all.

Before passing thevcurreut' through the line of electrodes each of the chambers of the furnace is closed at its ends by terminal blocks approximately fitting the rectangular cross section of the chamber. These terminal blocks are indicated at G G G2 and G.

The terminal G is connected to the positive cable and the terminal G to the negative cable. Th'eterminals G and G2 are connected to each other by means of a flexible cable H.

The column of electrodes vis surrounded by a heat retaining blanketl J which may be for example of pulverized charcoal. It is retained at the sides by longitudinal walls Avand the partition D and at the ends by terminal blocks G G G2 and G3. Preferably these blocks are arranged to make an' imperfect electrical connection with the adjacent ends of the electrodes. The blocks G and G3 are supported by struts K bearing against the adjacent end wall of the furnace. The opposite blocks G and G2, between which is the flexible connection H, are

aga-inst the ends of the e 'ec'trodes' Blocks M of wood or other yielding material are 'arranged behind the jacks so as to automatically provide for the expansion which vao follows.

occurs when the current is rst turned on' and for the shrinkage which subsequently f The construction of one of the blocks is shown in thessectioii View at G, Fig. l. A cup-shaped shell M of cast iron is cast with an encircling pipe therein for cooling it with4 water, and vwith prongsof wrought iron embedded in the bottom of the shell and projecting, therefrom to unite the shell firmlyto the filling of carbon within the shell. For securing a connection of exactly the desired degree. of conductivity or resistivity between'the ends of the electrodes E pressingv the electrodes together during the graphitizing process bymeans of the jacks L. The methodof introducing the graphite'-' is indicated in Fig. 3, The powdered charcoal J is first introduced to the level Q and the electrode E vlaid thereon, wit-ha strip R of paper, sheet metal or other flexible mav vterial passed around under the joint.. The

vends, ofthe strip are brought upward as shown. in full linesA after which4 the powdered charcoal .isintroduced-.to the level indicated in full lines, and the powdered graphite introduced` from t top and tamped sufciently to secure the desired -degree of compactnesa "I he -paper is then vbrought together in the manner indicated in dotted lines at R, and the powdered char--y coal raised to the level Qf and the graphite introduced to the same level; and so on un- 'til .the graphite is` introduced throughoutthe joint. The ends of the strip R. are then removed and the charcoal filled invupon the top` of the electrode to the desired height.

The jacks. .are then used to compress the joints to the desired degree o'f compactness. and the currentA is applied.

Fig: l-shows the connecting'ends of two of the electrodes E, the heavier shading in'- dicating 'the greater degree of graphitiza4 tion `at the ends. The connection is -made What I claim is:- I preferably use powdered graphite and in'- troduceit between theendsof the electrodes,

in thiscase by turning an external thread on lother and screwing the two parts firmly toj gether. Otherknownor suitable styles of connection may be used. The invention may lbe applied` to the making of one-piece electrodes, large or smal1`,vas well as to the -'inaking of thev electrodes or electrode sections shown which are intended for the subsequent. manufacture -of compound elec- 1 In aspecic lexample of. the` process the electrodes 'maybe of 'about twenty inches diameter or equivalent cross section. A current of 20,000 amperes may be used. The

contact betweentheadjacent ends of electrodes may be roughly about ten times as re- Y sistant as are the solid electrodes, and the desired degree of resistivity. may be Secured by using crushed'graphite of suitable fineness.

1. The method of raphitizing an-electrode .which consists in subJecting an end of the electrode to imperfect contact with a resistant conductor, and passing a suiiicient.

currentthrough the electrode and such resistant conductor, whereby sich end of the j electrode is heated to graphitizing tempera ture while the remainder of the electrode 1 heated to a lower temperature.

2. -The method of graphitiz'ing electrodes which'consists in.- arranging'them end to end with imperfect Contact, subjecting them to longitudinal pressure and' passing a current throu hthem'to'graphitize their c ontacting en s.

3. The method of graphitizing electrodes which consists in varranging them end' to.

end Awith an intervening resistant-packing aording imperfect contact, subjecting Lthem to longitudinal pressure and passing a currentthrough them to. graphitize their contactingUends. U

4. An 'electrode made up ofsections Joint-- ed together, the joined-ends of which are graphitized and other parts of which are not graphitized to the. saine extent.

In witness whereof, I'. have hereunto signed my name in the presenceof two subscribng witnesses.

PAUL LOUIS Witnesses: f v

D. ANTHONY'USINA, FRED WHITE.

TOUSSAINT HROULT. y 

